A layered double hydroxide (LDH) with nitrate as the counter anion (LDH-NO 3 with Mg/Al = 3) was, for the first time, successfully delaminated in formamide under ultrasonic treatment. Atomic force microscopy (AFM) images showed that a large part of the LDH was delaminated into single and double brucite layers (0.7-1.4 nm in thickness). The nano-sheets had disk-like shapes with a diameter of ca. 20-40 nm. Findings from AFM were in good agreement with the average hydrodynamic diameter determined using dynamic light scattering. Powder X-ray diffraction pattern of LDH dispersed in formamide also confirmed that LDH-NO 3 was exfoliated. The dispersions of LDH in formamide were stable and transparent up to a concentration of 40 g L 21 . However, formation of transparent gels was observed at concentrations higher than 5 g L 21 . Delaminated LDH could be restacked by adding sodium carbonate or ethanol.

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Measurements of soil particle‐size distributions have been performed down to 20‐nm radius using, beside classical methods such as sieving and sedimentation, mainly static and dynamic light scattering. The number of particles N per unit volume with a radius larger than r was found to follow a power law N α r−v with the exponent v = 2.8 ± 0.1. This exponent was observed in all soils investigated and can be interpreted as the fractal dimension of an underlying structure. The power law usually held over two to five decades of length scales. Below the lower cut‐off, typically located around 50 to 100 nm, the number of particles (≃ 1016‐1019 cm−3) remained roughly constant. Above the upper cut‐off, typically between 10 and 5000 µm, the distribution fell off much more steeply, possibly also like a power law with an exponent v = 5.4 ± 0.2.

We report a simple ultrasonic-assisted ion-exchange/intercalation process that enables unwrapping onedimensional (1D) titanate nanotubes into two-dimensional (2D) titanate nanosheets. The existence of this 1D to 2D topotactic transformation reveals that the titanate nanotubes could be considered as quasi-2D crystallites with excellent 2D properties such as exfoliation/delamination reactivities although they have the 1D morphology. The resulting titanate nanosheets possess larger band gap energy (∼3.75 eV) than that of the original nanotubes (∼3.30 eV), which might be attributed to the quantum size effect within the 2D titanate nanosheets with small thickness.

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